What is the maximum force a deep space spacecraft experiences after launch?

Question

The premise of How much of a deep space spacecraft's structural mass is useless dead weight after launch? Any plans to shed it in the future? is that the forces a deep space spacecraft experiences during launch and interplanetary trajectory insertion are much much larger than any forces it experiences ever again, at least until the last moments of end of mission.

Question: *What is the maximum force a deep space spacecraft experiences after launch?

Without a General Products Hull a spacecraft will experience tidal forces during flybys (gravity gradients across the craft itself), but I think that these are pretty tiny. Solar photon and solar winds are going to be tiny too, as are most micrometeorite impacts, though there may be some survivable impacts that are potentially consequential from a structural point of view.

I'm guessing that the biggest ones are always thrust from chemical engines during deep space and orbital insertion maneuvers. So the biggest one of those might be the answer.

Answer 1

In theory, there is no upper limit to the maximum force a spacecraft could experience in deep-space.

In practice, spacecraft design to orbit other planets will experience a large force during the orbit insertion manoeuvre. As an example, the Mars Reconnaissance Orbiter (MRO) used 6x 170 N engines for Mars Orbit Insertion (MOI), which would provided a combined thrust of just over 1 kN.

Planetary spacecraft can also experience non-negligible forces if they undergo aerobraking. Using MRO as another example, the maximum force experience during aerobraking would be ~13 N, assuming a maximum dynamic pressure limited to 0.35 N/m2 and an effective area of ~37 m2 (according to numbers in this paper).

Note that these forces are absolutely nothing compared to what is experienced during the launch phase as stated in the initial premise of your question.

There is one exception however that comes to mind.

NASA's Double Asteroid Redirection Test (DART) mission launched in November 2021. This spacecraft is set to deliberately crash into the minor-planet moon Dimorphos of the double asteroid Didymos as an experiment to measure the deflection of the impacting body.

According to the numbers in this link, DART will impact Dimorphos with a velocity of 6.6 km/s. At the time of impact the mass of DART will be about 550 kg. So, considering Newton's second law we can estimate the force on the spacecraft from the rate of change of momentum.

Assuming that the spacecraft takes 0.001 seconds to come to rest on the surface of Dimorphos (and I am using the term 'rest' very generously here), this would equate to a force experienced of the order of 3-4 Giga-Newtons!